Reverse phase connective tissue repair composition

ABSTRACT

A biocompatible connective tissue repair composition which comprises a therapeutic material and a carrier comprising a means for achieving reverse phase characteristics, and methods for using said composition. The therapeutic material can be demineralized bone powder, and the carrier can be a poloxamer such as poloxamer 407.

FIELD OF THE INVENTION

[0001] This invention concerns prosthetic materials. More particularly,it concerns a biocompatible material that exhibits reverse phasebehavior.

BACKGROUND ART

[0002] Osteogenic bone repair materials are known in the art. Thesematerials contain an osteogenic material, such as demineralized bonepowder in a carrier, such as glycerol. See, e.g., U.S. Pat. No.5,290,558, issued Mar. 1, 1994 to O'Leary et al., and U.S. Pat. No.5,284,655, issued Feb. 8, 1994 to Bogdansky et al.

[0003] The carrier of the bone material in the art is a liquid, having aviscosity generally somewhere between runny to paste-like. “Runny” bonerepair compositions have the advantage of being relatively easy to applyto and fill a bone defect, however, they are disadvantageous in that thematerial also tends to readily flow from the defect site. Conversely,bone repair compositions with a “paste-like” consistency are harder toapply to a defect, yet tend to remain positioned at the defect onceapplied. Additionally, when any of the bone repair compositions in theart are placed in vivo and become warmed, they become even less viscous;the decease in viscosity is due to the addition of thermal energy to thecomposition.

[0004] Accordingly, there is a need for a bone repair composition thatis easy to apply to a defect site, and which remains positioned at thesite once placed at the site.

DISCLOSURE OF THE INVENTION

[0005] Disclosed is a biocompatible composition to facilitate repair ofconnective tissues. The composition can comprise demineralized bonepowder, and, a carrier comprising a means for achieving reverse phasethermodynamic characteristics when mixed with the bone powder. Thecomposition can be substantially liquid at 0° C., and substantially moreviscous at 35° C., such that the composition has a consistency like thatof paste floor wax or like solid shoe wax. The means for achievingreverse phase characteristics can comprise a block copolymer, such as apoly(oxyalkylene) block copolymer, which can be apoly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblockcopolymer. The triblock copolymer can be a compound of the formula:

[0006] The means for achieving reverse phase characteristics comprises apoloxamer, such as poloxamer 407. The block copolymer can be a soliddissolved in a biocompatible solvent such as sterile water.

[0007] Preferably, the composition comprises a carrier of 25 weightpercent of a block copolymer dissolved in 75 weight percent of abiocompatible solvent. To vary the consistency of the composition, theweight percentage of demineralized bone powder or other solid can bevaried relative to the weight percentage of the carrier in thecomposition. For example, a paste-like form of the composition comprises50 weight percent of bone powder and 50 weight percent of a carriersolution. A gel-like embodiment of the composition comprises 70 weightpercent of bone powder and 30 weight percent of a carrier solution.

[0008] The bone powder of the composition can comprise particles with amedian length to a median thickness ratio of about 1.742:1, a meanlength of 0.25-1 mm (250-1,000 microns), and a mean thickness of about0.5 mm (500 microns).

[0009] Also disclosed is a method to facilitate the development of bonetissue, said method comprising: providing a biocompatible connectivetissue repair composition comprising demineralized bone powder, and, acarrier comprising a means for achieving reverse phase thermodynamiccharacteristics when mixed with the bone powder; and, placing thecomposition in a bony defect of a mammal. A prosthetic object can alsobe placed in the bony defect. The method can also comprise coating aportion of the prosthetic object with the biocompatible composition, andin this embodiment the step of placing the composition and the step ofplacing a prosthetic object can be contemporaneous.

MODES FOR CARRYING OUT INVENTION

[0010] Definitions

[0011] By “reverse phase” or “reverse thermal behavior” is intended amaterial that exhibits a physical property of becoming more viscous orsolidified upon addition of thermal energy. It is believed that thesolidification occurs by a mechanism other than that due to evaporationand corresponding loss of liquid.

[0012] As used herein, “ambient temperature” is 25° C., plus or minus 5°C.

[0013] As used herein, “body temperature” is 37° C., plus or minus 5° C.

[0014] As used herein, a “bony defect” or “bone defect site” is bonyenvironment of a mammal which comprises some viable bone tissue. Thedefect can be congenital, caused by trauma, or caused by disease.

[0015] “Osteoinductive” materials cause undifferentiated cells todifferentiate into a committed bone cell lines.

[0016] “Osteoinductive” materials provide support for cells of a bonecell lineage, e.g., permitting cells of a bone cell lineage to growalong or through a matrix or lattice.

Preferred Modes

[0017] In a preferred embodiment, the composition of the presentinvention is a flowable liquid when applied to a bony defect, whereuponthe composition becomes increasingly solidified or viscous as it warmsto ambient and is further solidified as it warms to body temperature.Upon being warmed to body temperature, a preferred composition of theinvention is a solid or highly viscous fluid. The reverse phasecompositions in accordance with the invention are significantlydifferent in principle from bone repair materials in the art, and do notfunction in the same way.

[0018] The composition comprises a therapeutic material for treating oneor more connective tissues; and, a carrier. The therapeutic material canbe a material to facilitate repair of connective tissues, i.e., a“connective tissue repair material.” The carrier achieves reverse phasecharacteristics when mixed with the therapeutic material.

[0019] The therapeutic material can be a material that isosteoinductive, osteoconductive, or a material that is osteoinductiveand osteoconductive. The therapeutic material can be xenogeneic,allogeneic, or autogenic. The therapeutic material can be alloplastic.As appreciated by one of ordinary skill in the art, the therapeuticmaterial can comprise combinations of various therapeutic materials.

[0020] Examples of osteoinductive material include but are not limitedto bone powder (mineralized or demineralized), tissue growth factor beta(TGF-β) types 1 through 13, bone morphogenetic protein (BMP) types 1through 15, or combinations thereof.

[0021] Examples of therapeutic materials that are osteoconductiveinclude but are not limited to xenogeneic bone (mineralized ordemineralized); the xenogeneic bone can also be subjected todeproteination. Presently preferred xenogeneic source are porcine andbovine.

[0022] Therapeutic materials that are osteoinductive and osteoconductiveinclude particulate human allograft, e.g., of demineralized bone.

[0023] Examples of alloplastic materials comprise gypsum, corallinehydroxyapatite, synthetic hydroxyapatite, calcium carbonate, calciumphosphate, calcium sulfate, biodegradable polymeric materials, orcombinations thereof.

[0024] A presently preferred composition comprises demineralizedosteogenic bone powder in a carrier; the composition can be applied to abone defect site to induce new bone growth. This composition of thepresent invention comprises demineralized bone particles or granules(referred to herein as “demineralized bone powder”) in an inertbiocompatible carrier.

[0025] In a preferred embodiment, the particles/granules have a medianlength to median thickness ratio about 1.742:1, a mean length of 0.25-1mm (250-1,000 microns) and a mean thickness of about 0.5 mm (500microns).

[0026] The presently preferred biocompatible carrier of the compositionof the invention is a material that confers reverse phase thermodynamicproperties on the composition. The use of PLURONIC® F127 as a componentof an osteointegration promoting composition is set forth in U.S. Pat.No. 5,503,558, issued Apr. 2, 1996 to the inventor herein, Cameron C. L.Clokie; and in PCT International Publication No. WO 95/13099. In apresently preferred embodiment, the carrier comprises a polymer marketedby BASF (Parsipanny, N.J.) as PLURONIC® F127. PLURONIC® F127 is apoly(oxyalkylene) block copolymer; more specifically, apoly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) poly(oxyethylene)triblock copolymer; it is a member of a class of compounds calledpoloxamers. (Schmolka, “A Review of Block Polymer Surfactants” J. Am.Oil Chemists Soc. 54:110-116 (1977)). Several members of the poloxamerfamily exhibit reverse phase thermodynamic characteristics. PLURONIC®F127 is also known by the name “poloxamer 407.” (Schmolka, “A Comparisonof Block Polymer Surfactant Gels” J. Am. Oil Chemist Soc. 68:206-209(1991)). PLURONIC® F127 has an-average molecular weight of approximately12,500. (Schmolka, “A Comparison of Block Polymer Surfactant Gels” J.Am. Oil Chemist Soc. 68:206-209 (1991)) The structure of the PLURONIC®F127 polymer is depicted as follows:

[0027] In preferred embodiments of a composition of the presentinvention, the carrier is a liquid diluted in a solvent or is a soliddissolved in a solvent. In one embodiment, PLURONIC® F127 is dissolvedin a solvent such as sterile water. The PLURONIC® F127 carrier is vastlydifferent in size, molecular weight, and chemical structure thancarriers in the art. The carrier is also substantially different interms of its functional properties than any carrier of a bone repairmaterial in the art.

[0028] The proposed composition has a unique physical property, beingflowable at refrigerated temperatures and increasingly solidified atelevated temperatures, such as ambient and body temperatures. Thisproperty is referred to in the art as “reverse phase” or “reversethermal behavior”. Due to the reverse phase property of the proposedcomposition, the composition is generally manufactured at refrigeratedtemperatures, such as 5° C. Manufacturing is done at refrigeratedtemperatures to enhance mixing of the components of the composition,since the proposed composition comprising an aqueous solution ofPLURONIC® F127 begins to become more viscous at ambient temperature, andis increasingly viscous and solidified at body temperature. Generally, acomposition of the invention will be twice as viscous at 35° C. as it isat 0° C.

[0029] For example, the preferred PLURONIC® F127 carrier in thecomposition of the present invention (when dissolved in an appropriateamount of sterile water), has the unique property of being a liquid atambient temperature and increasingly solidified, then solid at elevatedtemperature, absent the effects of evaporation and concomitant loss ofwater. This property is called “reverse phase” or “reverse thermalbehavior” because it is the exact opposite of the thermodynamicproperties exhibited by standard carriers.

[0030] It is believed that the reverse phase property is due, at leastin part, to the fact that PLURONIC® F127 is composed of discrete blocksof both hydrophilic (i.e., oxyethylene) and hydrophobic (i.e.,oxypropylene) subunits. (See e.g., Schmolka, “A Comparison of BlockPolymer Surfactant Gels” J. Am. Oil Chemist Soc. 68:206-209 (1991)).

[0031] In contrast, standard carriers, as well as all liquids, manifestthe typical physical property of becoming increasingly flowable uponaddition of thermal energy, such as occurs when the liquid is heated tobody temperature. However, the preferred carrier in a composition of thepresent invention becomes less flowable as energy is added to it eitherby heating or by shaking.

[0032] The unique reverse phase thermodynamic properties of thecomposition of the present invention allow the product to function in asubstantially different, and preferred manner relative to other flowablebone repair products. When applied to a bone defect site, the reversephase property of the preferred carrier provides support characteristicsfor the composition which are substantially different than thecharacteristics of standard carriers. Enhanced support is provided bythe composition of the invention. The preferred PLURONIC® F127 carrierof the composition of the present invention helps to provide supportcharacteristics which are unlike those of any standard carrier. This isbecause the composition is flowable at ambient temperature and can thusreadily be applied to a bony defect site, but it becomes increasinglyviscous and solidified once it is warmed at the site. The solidificationof the composition of the present invention achieves several; beneficialeffects. When solidified, the composition does not flow away from thedefect site, and the solidified product immediately augments andfacilitates structural support at the defect. Also, since the osteogeniccomposition of the invention is initially liquid, it readily fills adefect, then becomes solidified and achieves enhanced osteogenesis.Moreover, with preferred compositions of the invention, comprising asterile aqueous solution of PLURONIC® F127 as carrier and demineralizedbone powder, the carrier will resorb or dissolve after about three days,leaving the osteogenic bone powder at the bone defect site. It isbelieved to be advantageous that the carrier dissolves as this thenallows for enhanced ingrowth of connective or vascular tissues.

[0033] In a composition of the invention, the weight percentages of thetherapeutic material and the carrier can each be varied. For example,the weight percent of the therapeutic material can vary between about 20to 80 weight percent of the composition, and the weight percent of thecarrier can vary between about 20 to 80 weight percent of thecomposition. Furthermore one or more additional components can bepresent in a composition of the invention, such as antibiotics,analgesic, anti-inflammatory agents, or agents to promote development ofconnective or circulatory system tissues.

EXAMPLES Example 1

[0034] To obtain a composition having a gel-like consistency, thecomposition comprised 70 weight percent of a solution of PLURONIC® F127and 30 weight percent of bone powder. In this example, the carriercomprised 25 weight percent of PLURONIC® F127 powder dissolved in 75weight percent sterile water.

[0035] A composition of the invention is available as DynaGraft™ Gel(GenSci Regeneration Laboratories, Inc., Irvine, Calif.); this productis a composition comprising demineralized allograft bone from a singledonor mixed with an inert preservative and a biocompatible carrier. Thecomposition has a “gel” consistency and is provided in a sterile, singlepatient use package.

[0036] The tissues used in the bone repair composition are recovered byUnited States tissue banks, from carefully screened donors, according tostandards established by the American Association of Tissue Banks. Allsuch tissues meet stringent specifications during donor screening andlaboratory testing in order to reduce the risk of transmitting anyinfectious disease.

[0037] For example, each donor is tested and found to be negative for(at a minimum): hepatitis B surface antigen, human immunodeficiencyvirus 1 and 2 antibodies, HTLV-1 antibody, hepatitis C virus antibody,and syphilis. The tests were performed by a CLIA approved laboratoryutilizing FDA-licensed test kits. The medical and social history of thedonor revealed no risk factors for, or clinical evidence of, HIV orhepatitis infection.

[0038] This biocompatible composition in accordance with the inventionwas produced under environmentally controlled conditions using stringentcleaning, preservation, and sterilization procedures. All steps arerigorously quality controlled in accordance with accepted methodologiesin the art.

[0039] DynaGraft™ Gel is indicated for use in surgical procedures inwhich osteogenesis, calcification or bony fusion is needed to achieve orenhance the quality of the final result. Accordingly, DynaGraft™ Gel canbe used in a variety of orthopedic, reconstructive, and dental bonegrafting procedures. DynaGraft™ Gel may be used alone as a bone graft incases in which the graft is not intended to provide weight bearingsupport or dimensional integrity to the graft site. If the graft isintended to be weight bearing, the composition should be used withappropriate fixation. DynaGraft™ Gel can, therefore, be used as acomplement to musculoskeletal implants such as joint replacementprostheses, intraoral implants, and internal and external fixationdevices for procedures in which demineralized freeze-dried boneallograft would be used.

[0040] The composition is sterilized by a targeted 2.5 megarads ofelectron beam irradiation as terminal sterilization. When implanting thecomposition, sterile technique should be maintained to minimize the riskof post-operative complications. Use of the composition iscontraindicated when there is active or latent infection at or near thesurgical site.

[0041] The composition should be stored long-term in a clean, dry placeat room temperature. It should be kept out of direct sunlight and shouldnot be frozen. DynaGraft™ Gel does not require rehydration prior to use.

[0042] The packaging of all DynaGraft™ implant compositions has beenspecially designed to provide ease of use within the surgical field. Forexample, the composition can be packaged within syringes that are keptsterile within one or more foil containers. DynaGraft™ Gel is suppliedin 1.0 cc, 5 cc, and 10 cc syringes.

[0043] To use the composition packaged in syringes within foilcontainers, the packaging is opened by peeling open the outer foil and,using sterile technique, transferring the entire inner package to thesterile field. The inner package is then opened and the syringe removed.Immediately before use, a protective cap which covers the tip of thesyringe is removed. The composition is then extruded by pushing on thesyringe plunger to deliver the desired volume. Appropriate placementand/or fixation are critical factors in the avoidance of potentiallyadverse effect on product service life.

[0044] Accordingly, the DynaGraft™ Gel is bacteriologically sterileduring the stated shelf life in an unopened and undamaged package. Theproduct must be used before the expiration date. Unused product shouldbe properly discarded.

Example 2

[0045] To obtain a composition having a paste-like consistency, thecomposition comprised 50 weight percent of a solution of PLURONIC® F127and 50 weight percent of bone powder. In this example, the carriercomprised 25 weight percent of PLURONIC® F127 powder dissolved in 75weight percent sterile water.

[0046] A composition of the invention is available as DynaGraft™ Putty(GenSci Regeneration Laboratories, Inc., Irvine, Calif.); this productis a composition comprising demineralized allograft bone from a singledonor mixed with an inert preservative and a biocompatible carrier. Thecomposition has a “putty-like” consistency and is provided in a sterile,single patient use package.

[0047] The tissues used in the bone repair composition are recovered byUnited States tissue banks, from carefully screened donors, according tostandards established by the American Association of Tissue Banks. Allsuch tissues meet stringent specifications during donor screening andlaboratory testing in order to reduce the risk of transmitting anyinfectious disease.

[0048] For example, each donor is tested and found to be negative for(at a minimum): hepatitis B surface antigen, human immunodeficiencyvirus 1 and 2 antibodies, HTLV-1 antibody, hepatitis C virus antibody,and syphilis. The tests were performed by a CLIA approved laboratoryutilizing FDA-licensed test kits. The medical and social history of thedonor revealed no risk factors for, or clinical evidence of, HIV orhepatitis infection.

[0049] This biocompatible composition in accordance with the inventionwas produced under environmentally controlled conditions using stringentcleaning, preservation, and sterilization procedures. All steps arerigorously quality controlled in accordance with accepted methodologiesin the art.

[0050] DynaGraft™ Putty is indicated for use in surgical procedures inwhich osteogenesis, calcification or bony fusion is needed to achieve orenhance the quality of the final result. Accordingly, DynaGraft™ Puttycan be used in a variety of orthopedic, reconstructive, and dental bonegrafting procedures. DynaGraft™ Putty may be used alone as a bone graftin cases in which the graft is not intended to provide weight bearingsupport or dimensional integrity to the graft site. If the graft isintended to be weight bearing, the composition should be used withappropriate fixation. DynaGraft™ Putty can, therefore, be used as acomplement to musculoskeletal implants such as joint replacementprostheses, intraoral implants, and internal and external fixationdevices for procedures in which demineralized freeze-dried boneallograft would be used.

[0051] The composition is sterilized by a targeted 2.5 megarads ofelectron beam irradiation as terminal sterilization. When implanting thecomposition, sterile technique should be maintained to minimize the riskof post-operative complications. Use of the composition iscontraindicated when there is active or latent infection at or near thesurgical site.

[0052] The composition should be stored long-term in a clean, dry placeat room temperature. It should be kept out of direct sunlight and shouldnot be frozen. DynaGraft™ Putty does not require rehydration prior touse.

[0053] The packaging of all DynaGraft™ implant compositions has beenspecially designed to provide ease of use within the surgical field. Forexample, the composition can be packaged within jars that are keptsterile within one or more foil containers. DynaGraft™ Putty Gel issupplied in 2.5 cc, 5-cc, and 10 cc jars.

[0054] To use the composition packaged in jars within foil containers,the packaging is opened by peeling open the outer foil and, usingsterile technique, transferring the entire inner package to the sterilefield. The inner package is then opened and the jar and a spatula areremoved. The jar lid is opened in a sterile manner and composition puttyis removed with the spatula or other hand-held instrument.

[0055] Appropriate placement of the composition and/or fixation arecritical factors in the avoidance of potentially adverse effects onproduct service life.

[0056] Accordingly, the DynaGraft™ Putty is bacteriologically sterileduring the stated shelf life in an unopened and undamaged package. Theproduct must be used before the expiration date. Unused product shouldbe properly discarded.

[0057] Closing

[0058] It must be noted that as used herein and in the appended claims,the singular forms “a,” “and,” and “the” include plural referents unlessthe context clearly dictates otherwise. Thus, for example, reference to“a formulation” includes mixtures of different formulations andreference to “the method of treatment” includes reference to equivalentsteps and methods known to those skilled in the art, and so forth.

[0059] Unless defined otherwise, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this invention belongs. Although any methodsand materials similar to or equivalent to those described herein can beused in the practice or testing of the invention, the preferred methodsand materials are now described. All publications mentioned herein arefully incorporated herein by reference.

What is claimed is:
 1. A biocompatible connective tissue repaircomposition comprising: demineralized bone powder, and, a carriercomprising a liquid poloxamer solution or a solid poloxamer dissolved ina solvent, whereby said carrier achieves reverse phase characteristicswhen mixed with the demineralized bone powder.
 2. The composition ofclaim 1, whereby the carrier causes the composition to be substantiallyliquid at 0° C., and substantially solid at 35° C.
 3. The composition ofclaim 1 which has a first viscosity at 0° C., and a second viscosity at35° C., wherein the second viscosity is at least twice as great as thefirst viscosity.
 4. The composition of claim 1, wherein carriercomprises a solid poloxamer dissolved in a solvent, and the poloxamer ispoloxamer
 407. 5. The composition of claim 4 wherein the solvent issterile water.
 6. The composition of claim 5 wherein 25 weight percentof the poloxamer 407 is dissolved in 75 weight percent of the sterilewater.
 7. The composition of claim 1, wherein 30 weight percent of thebone powder is dispersed in 70 weight percent of the carrier.
 8. Thecomposition of claim 1, wherein 50 weight percent of the bone powder isdispersed in 50 weight percent of the carrier.
 9. The composition ofclaim 1 wherein the bone powder comprises particles with a median lengthto a median thickness ratio of about 1.742:1, a mean length of 0.25-1 mm(250-1,000 microns), and a mean thickness of about 0.5 mm (500 microns).10. A biocompatible connective tissue repair composition comprising: atherapeutic material, and, a carrier comprising a means for achievingreverse phase characteristics.
 11. The composition of claim 10, whereinthe therapeutic material is osteoinductive, osteoconductive, orpsteoinductive and osteoconductive.
 12. The composition of claim 10,wherein the therapeutic material is alloplastic, xenogeneic, allogeneic,or autogenic.
 13. The composition of claim 10, whereby the means forachieving reverse phase characteristics causes the composition to besubstantially liquid at 0° C., and substantially solid at 35° C.
 14. Thecomposition of claim 10 which has a first viscosity at 0° C., and asecond viscosity at 35° C., wherein the second viscosity is at leasttwice as great as the first viscosity.
 15. The composition of claim 10,wherein the means for achieving reverse phase characteristics comprisesa poloxamer.
 16. The composition of claim 15, wherein the means forachieving reverse phase characteristics comprises poloxamer
 407. 17. Thecomposition of claim 10, wherein the means for achieving reverse phasecharacteristics comprises a block copolymer.
 18. The composition ofclaim 17, wherein the means for achieving reverse phase characteristicscomprises a poly(oxyalkylene) block copolymer.
 19. The composition ofclaim 18, wherein the means for achieving reverse phase characteristicscomprises a poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene)triblock copolymer.
 20. The composition of claim 19, wherein thetriblock copolymer comprises a formula:


21. The composition of claim 17, wherein the block copolymer is a solidand is dissolved in a biocompatible solvent.
 22. The composition ofclaim 21, wherein the biocompatible solvent is sterile water.
 23. Thecomposition of claim 21, wherein 30 weight percent of the therapeuticmaterial is dispersed in 70 weight percent of the carrier.
 24. Thecomposition of claim 21, wherein 50 weight percent of the therapeuticmaterial is dispersed in 50 weight percent of the carrier.
 25. Thecomposition of claim 10 wherein the therapeutic material comprises bonepowder, and the bone powder comprises particles with a median length toa median thickness ratio of about 1.742:1, a mean length of 0.25-1 mm(250-1,000 microns), and a mean thickness of about 0.5 mm (500 microns).26. A method to facilitate the development of bone tissue, said methodcomprising: providing the composition of claim 10; and, placing thecomposition in a bony defect of a mammal.
 27. The method of claim 26,further comprising a step of placing a prosthetic object in the bonydefect.
 28. The method of claim 27, wherein the composition coats aportion of the prosthetic object, and the step of placing thecomposition and the step of placing a prosthetic object arecontemporaneous.